The present invention relates to a chromatographic separator and more particularly to the concentration sensor disposed in an intermittently-moving-bed chromatographic separator.
In manufacturing industries such as the sugar industry or the pharmaceutical industry, chromatographic separators are widely used to extract one or more components from fluid of a crude material consisting of a plurality of components and obtained from nature or through chemical reactions. Among the chromatographic separators, a variety of moving-bed separators have been proposed other than the batch fixed-bed separators conventionally used.
FIG. 4 is a schematic cross-sectional view illustrating a separation vessel, showing the principle of a typical chromatographic separator employing the moving-bed scheme. The separation vessel 60 is filled with a filler (adsorbent) 62 in advance, and is full of liquid eluent therein. A feed liquid material including two species of components A and C is introduced from a feed liquid material supply port F, and the liquid eluent is supplied from a liquid eluent supply port D at a constant linear speed. Each of the components A and C moves at different linear speeds within the separation vessel 60 due to the difference in affinity for the filler. For example, the component A having a lower affinity moves at a higher linear speed, whereas the component C having a higher affinity moves at a lower linear speed. Accordingly, by discharging the circulating liquid from two appropriate positions, the feed liquid material can be separated into a liquid containing more of the component A (hereinafter simply referred to as the component A) and a liquid containing more of the component C (hereinafter simply referred to as the component C).
A chromatographic separator employing the moving-bed scheme creates the movement of the filler, in the direction opposite to the flow of the liquid eluent, at a speed between the speed of movement of the component A and that of the component C. As shown in the figure, this makes it possible to take out the components at respective positions across the supply position of the feed liquid material. That is, as viewed from the direction of the flow of the circulating liquid, the component A can be taken out the feed liquid material supply position F and the component C can be taken out in front of the feed liquid material supply position F. In this scheme, since it is difficult to allow the filler to move at a uniform speed, it is not feasible to use this scheme in commercial applications.
A separator has been in practical use which is capable of obtaining the separation performance equivalent to that of a separator employing the foregoing moving-bed scheme, without allowing the filler to move. FIG. 5 illustrates the principle of this type of separator. In this scheme, the separation vessel 60 is divided into a plurality of columns 64 (twelve columns in the example of the figure), which are coupled to form an endless circular path. Instead of the movement of the filler, the feed liquid material supply position F and the liquid eluent supply position D and the discharge positions of the components A and C are shifted in the direction of flow of the liquid eluent. As time elapses, the distribution of the liquid in the system is shifted in the direction of the circulating liquid. When the concentration distribution has been shifted by a distance corresponding to one column after a certain period of time, the supply positions of the feed liquid material and the liquid eluent and the discharge positions of the components A and C are shifted in the direction of the circulating liquid by the distance corresponding to one column. The repetition of this operation makes it possible to supply and discharge each of the liquids at the optimum position at any time. Three schemes are employed to shift the supply positions of the feed liquid material and the liquid eluent and the discharge positions of the components A and C. The schemes, now in practical use, include a simulated moving-bed scheme in which liquid injection valves and liquid discharge valves, such as electromagnetic valves, are assembled and switched sequentially; another simulated moving-bed scheme in which a rotary valve having a number of nozzles is used and an intermittently-moving-bed scheme in which a rotary valve having a number of nozzles is used while moving the separation vessel.
The supply positions of the feed liquid material and the liquid eluent, and the discharge positions of the components A and C are preferably shifted or these steps are preferably switched in accordance with the concentration distributions of the components A and C in the circular path. That is, it is preferable to measure the concentration distribution in the circular path to adjust the positions for supplying and discharging the liquids and to adjust the timing for supplying the feed liquid material and the liquid eluent in accordance with the measured concentrations. Conventionally, however, such controls were typically performed in accordance with a specified time schedule instead.
A simulated moving-bed chromatographic separator, which uses the simulated moving-bed scheme employing a rotary valve having a number of nozzles, is described in Japanese Patent Laid-Open Publication No. Hei 9-206502. The simulated moving-bed chromatographic separator has a concentration sensor disposed between columns to correct the time schedule in accordance with a signal given from the concentration sensor. According to this scheme, the supply positions of the feed liquid material and the liquid eluent, the discharge positions of the components A and C, and the amount of supplied liquids can be controlled in accordance with the results of measurement of concentration. Thus, the separation efficiency of the chromatographic separator is improved.
The simulated moving-bed chromatographic separator described in the foregoing publication employs such a scheme so as to allow the columns to be stationary and the rotary valve to shift the positions for supplying and discharging each liquid. Thus, a concentration sensor can be readily installed in the circular path. However, in the intermittently-moving-bed chromatographic separator, which shifts the filled columns by using the rotary valve having a number of nozzles, in order for allowing the concentration sensor to be installed in an appropriate position between columns, it is necessary to install a dedicated rotary valve between a column and the concentration sensor to thereby introduce the liquid flow in the circular path to the concentration sensor.
Installation of the dedicated rotary valve for the concentration sensor, however, complicates the structure of the circular path of the chromatographic separator, raises the cost of the separator, and also degrades the separation performance. Consequently, no concentration sensor was conventionally used in this type of the chromatographic separator.
In view of the above, it is an object of the present invention to improve the intermittently-moving-bed chromatographic separator which shifts the filled columns by using a rotary valve having a number of nozzles, and to provide a chromatographic separator which is capable of improving the separation performance thereof by disposing a concentration sensor therein at an appropriate position to adjust the control of the separator in accordance with the results of the measurement by the concentration sensor.
The present invention provides an intermittently-moving-bed chromatographic separator including: a rotary valve including a stationary member having a substantially cylindrical or disc surface mounting thereon a plurality of stationary nozzles, and a rotary member having a rotary surface slidably rotating on said cylindrical or disc surface intermittently at a specified timing, said rotary surface mounting thereon rotary nozzles intermittently communicated with said stationary nozzles, said rotary member supporting at least four columns en bloc each having an inlet port and an outlet port so that said rotary nozzles are communicated with said inlet ports and said outlet ports, said stationary nozzles being coupled by a tube assembly to couple said columns in a circular path; first and second injection tubes for introducing a feed liquid material including first and second components and for introducing a liquid eluent, respectively; first and second discharge tubes coupled to said circular path to discharge said first and second components, respectively, from said first circular path; and a concentration sensor supported by said rotary member to be coupled to said circular path, said concentration sensor having an external terminal connected through a combination of slip-ring and a current collector to the outside.
The intermittently-moving-bed chromatographic separator according to the present invention is configured so that the concentration sensor is rotatably supported by the rotary member, and the leads from the concentration sensor are connected to the outside via slip rings and a current corrector. Therefore, the concentration sensor can be disposed at an appropriate position in the circular path and the fine control of the separator can be performed based on the results of measurement conducted therewith. Thus, the present invention can provide an improved separation performance for the intermittently-moving-bed chromatographic separator.